I’m not even sure Wizard society as a whole see mental disorders as a health problem — they seem to act as if mental problems are a moral weakness.
It does seem that way, doesn’t it? The general attitude of the Order seems to be, “Oh, there’s nothing wrong with Sirius, he’s just being a jerk.” Dumbledore’s remarks at the end about how Sirius was “too old and too clever” to be bothered by Snape’s verbal attacks comfirm that. The implication is that if Sirius didn’t behave sensibly, it was his own damn fault. But I think expecting Sirius to behave sensibly under the circumstances was like expecting a man with two broken legs to get up and walk. It just wasn’t going to happen.
Given the way Wizarding social attitudes seem to lag behind Muggle ones, I think Sirius found himself in the same situation that a lot of shell-shocked soldiers found themselves in during the early days of WWI: people who hadn’t been through the same experience didn’t believe that all these soldiers were really sick — they were just weak, or cowardly, and trying to get out of fighting.
This always bothered me immensely.
There were multiple references to Sirius’s brooding in Order of the Phoenix, and his moods seemed to generally be regarded by those around him as exactly that – moodiness, grumpiness, surliness. A state of emotion, certainly, but one can very obviously choose not to act grumpy or surly; the implication always seemed to be that he was being uncooperative, even childish, in being so obviously less than happy.
Even after or around Christmas – the joy of the festivities and having everyone around seems to die down, and his laughter gets more forced, he spends more time alone. Everyone is happy – why can’t Sirius be happy too? – who does he think he’s helping, honestly, with that constant raincloud over his head?
Except the truth seems to me to have been exactly the other way around. Except for a few times when he managed to be honestly overcome with joy, Sirius was in a constant state of depression because Sirius was chronically depressed. Any time he interacts, seems happy, acts the good host – that is him putting on the act for the sake of the people around them, their mutual happiness, and any chance he has left at appearing ‘normal’ and, God forbid, something other than useless.
Seeing him treated as a pissy child throwing a tantrum and trying to bring everyone’s mood down with his own just infuriates me, because the man was struggling with legit depression/PTSD.
It’s also worth noting that Dumbledore was taught from his own childhood that the best – indeed, the only – way to treat a psychologically broken person was to shut them away for their own protection and hope for the best. He did with Sirius and Harry what he learned, in Aberforth’s words, at his mother’s knee. Look at the closed ward in St Mungo’s, with the Longbottoms and Lockhart and Sturgis Podmore and the woman who could only bark. The Order may seem unsympathetic to Sirius, but they’re responding the only way they know how – let him have his moment and hope he improves later – because, as the quote suggests, the wizarding world really doesn’t get the concept of PTSD or mental illness. Luna is mocked for being ‘Loony’ when in the muggle world she’d have been prescribed counselling after seeing her mother die. Sirius even can’t safely access any better options – if he leaves the house (which keeps him safe physically while being quite possibly the worst possible place for him to be mental-health wise) he risks being caught and Kissed. Part of the tragedy of Sirius is that he could have been helped (and at the very least Harry, Remus and Tonks would have been eager to help him) if only those around him had known how.